Background <p>This study aimed to elucidate the relationships of psychological flexibility (PF) patterns in patients with type 2 diabetes mellitus with physiological and lifestyle indexes.</p> Methods <p>The study recruited 223 inpatients and outpatients for the survey. It focused on levels of experiential avoidance (EA) and subgroups of comprehensive PF patterns. The differences in self-care behavior and medical condition between high- and low-EA groups were examined using <i>t</i>-test or Wilcoxon’s rank sum test. Furthermore, ANOVA or Kruskal–Wallis test was conducted to depict group features after applying cluster analysis to extract PF patterns.</p> Results <p>Analyses revealed that low-EA patients exhibited better conditions. A subsequent cluster analysis extracted three subgroups: flexible, inaction, and entangled. The distinguishing characteristics were manifested in the patterns of fusion, values, and commitment. In general, the flexible subgroup exhibited optimal conditions that align with those reported in previous studies and theoretical assumptions of acceptance and commitment therapy.</p> Conclusion <p>Considering these findings and their commonality with previous research, the study recommended that assessments focusing on processes—specifically cognitive fusion, and values and commitment, in addition to EA—may yield valuable insights for healthcare providers and emphasize the potential utility of a tiered intervention guide that first targets fusion, followed by values and commitment.</p> Trial registration <p>Not applicable.</p>